Method of fabricating a spherical cavitation chamber

ABSTRACT

A method of fabricating a spherical cavitation chamber. Depending upon the chamber&#39;s composition and wall thickness, chambers fabricated with the disclosed techniques can be used with either low or high pressure systems. During chamber fabrication, initially two spherical half portions are fabricated and then the two half portions are joined together to form the desired cavitation chamber. During the fabrication of each chamber half, the interior spherical surface is completed first and then the outer spherical surface. Prior to joining the two spherical cavitation chamber halves, the surfaces to be mated are finished, preferably to a surface flatness of at least ± 0.01  inches. Brazing is used to join the chamber halves together. The brazing material is preferably in the form of a ring-shaped sheet with outside and inside diameters of approximately the same size as the cavitation sphere&#39;s outside and inside diameters. Preferably the brazing operation is performed under vacuum conditions. During brazing, preferably force is applied to the two half spheres in order to compress the brazing material and achieve a strong bond. In order to insure that the inner surface of the completed cavitation chamber is relatively smooth, means for aligning the two half spheres during brazing is required, the means being either integral or external to the half spheres.

FIELD OF THE INVENTION

The present invention relates generally to sonoluminescence and, moreparticularly, to a method of fabricating a sonoluminescence cavitationchamber.

BACKGROUND OF THE INVENTION

Sonoluminescence is a well-known phenomena discovered in the 1930's inwhich light is generated when a liquid is cavitated. Although a varietyof techniques for cavitating the liquid are known (e.g., sparkdischarge, laser pulse, flowing the liquid through a Venturi tube), oneof the most common techniques is through the application of highintensity sound waves.

In essence, the cavitation process consists of three stages; bubbleformation, growth and subsequent collapse. The bubble or bubblescavitated during this process absorb the applied energy, for examplesound energy, and then release the energy in the form of light emissionduring an extremely brief period of time. The intensity of the generatedlight depends on a variety of factors including the physical propertiesof the liquid (e.g., density, surface tension, vapor pressure, chemicalstructure, temperature, hydrostatic pressure, etc.) and the appliedenergy (e.g., sound wave amplitude, sound wave frequency, etc.).

Although it is generally recognized that during the collapse of acavitating bubble extremely high temperature plasmas are developed,leading to the observed sonoluminescence effect, many aspects of thephenomena have not yet been characterized. As such, the phenomena is atthe heart of a considerable amount of research as scientists attempt tonot only completely characterize the phenomena (e.g., effects ofpressure on the cavitating medium), but also its many applications(e.g., sonochemistry, chemical detoxification, ultrasonic cleaning,etc.). A by-product of this research have been several patents claimingvarious aspects of the process. One such patent, U.S. Pat. No.4,333,796, discloses a cavitation chamber that is generally cylindricalalthough the inventors note that other shapes, such as spherical, canalso be used. It is further disclosed that the chamber is comprised of arefractory metal such as tungsten, titanium, molybdenum, rhenium or somealloy thereof. U.S. Pat. No. 4,333,796 does not disclose any techniquesfor fabricating the chamber. Similarly U.S. Pat. No. 4,563,341, acontinuation-in-part of U.S. Pat. No. 4,333,796, does not disclosefabrication techniques for use with the disclosed cylindrical chamber.Rather, the patent simply discloses the preferred materials for thechamber walls and chamber linings and the preferred mounting locationsfor an array of acoustic horns.

U.S. Pat. No. 5,659,173 discloses a sonoluminescence system that uses atransparent spherical flask. The spherical flask is not described indetail, although the specification discloses that flasks of Pyrex®,Kontes®, and glass were used with sizes ranging from 10 milliliters to 5liters.

U.S. Pat. No. 5,858,104 discloses a shock wave chamber partially filledwith a liquid. The remaining portion of the chamber is filled with gaswhich can be pressurized by a connected pressure source. Acoustictransducers mounted in the sidewalls of the chamber are used to positionan object within the chamber. Another transducer mounted in the chamberwall delivers a compressional acoustic shock wave into the liquid. Aflexible membrane separating the liquid from the gas reflects thecompressional shock wave as a dilation wave focused on the location ofthe object about which a bubble is formed. The shape, composition andfabrication of the shock wave chamber is not disclosed.

U.S. Pat. No. 6,361,747 discloses an acoustic cavitation reactor. Thereactor chamber is comprised of a flexible tube through which the liquidto be treated circulates. The acoustic transducers are radiallydistributed around the tube. As disclosed, the reactor tube may becomprised of a non-resonant material such as a resistant polymericmaterial (e.g., TFE, PTFE), with or without reinforcement (e.g.,fiberglass, graphite fibers, mica).

Although not in the field of sonoluminescence, U.S. Pat. No. 4,448,743discloses a confinement chamber for use with an ultra-high temperaturesteady-state plasma. Although the plasma is referred to as a“plasmasphere”, the specification is unclear as to whether theconfinement chamber is spherical or cylindrical in nature. Furthermore amethod of fabricating the disclosed chamber is not provided. Rather, thepatent simply discloses the design requirements for such a chamber. Forexample, in describing the requirements for an isochoric heating system,the patent discloses that the vessel should be capable of containing apressure that is slowly increased from 1.82 atmospheres to 22.1atmospheres and be fitted with infrared and far-infrared windows as wellas a down-draft vertical hydrogen jet.

Although a variety of sonoluminescence systems have been designed,typically these systems are intended for low pressure research andtherefore are comprised of glass or similar material. Those designed forhigher pressures are usually cylindrically shaped. Those researchers whohave suggested the use of spherical chambers have not disclosed how tofabricate such a chamber to enable it to handle high pressure.Accordingly, what is needed is a method of fabricating a sphericalcavitation chamber that can be used for high pressure sonoluminescence.The present invention provides such a method.

SUMMARY OF THE INVENTION

The present invention provides a method of fabricating a sphericalcavitation chamber for sonoluminescence. Depending upon both thechamber's composition and wall thickness, chambers fabricated with thedisclosed techniques can be used with either low or high pressuresystems.

According to the invention, chamber half portions are first fabricatedand then the two half portions are joined together to form the desiredcavitation chamber. According to one embodiment, during the fabricationof each chamber half, the interior surface, the mating surface and aportion of the exterior surface are fabricated while the piece of stockis mounted within a first lathe chuck. The stock piece is thenun-mounted, reversed, and mounted within a second lathe chuck. Thesecond lathe chuck may be the same as the first lathe chuck, or thesecond lathe chuck may have jaws with holding surfaces which match thecurvature of the exterior surface of the chamber half. Once mountedwithin the second lathe chuck, the remaining portion of the exteriorsurface is turned. According to a second embodiment, during thefabrication of each chamber half the interior spherical surface iscompleted first along with a cylindrical portion. The stock piece isthen un-mounted, reversed, and remounted prior to turning the exteriorspherical surface. The cylindrical portion is then removed and themating surface finished.

According to another aspect of the invention, joining the half sphericalportions together is accomplished with a brazing material suitable foruse with the material comprising the half spheres. The brazing materialis preferably in the form of a ring-shaped sheet with outside and insidediameters of approximately the same size as the cavitation sphere'soutside and inside diameters. The two half spheres, with interposedbrazing material, are then placed in a suitable chamber which isevacuated and heated to a temperature above the melting temperature ofthe brazing material. During the brazing operation, preferably force isapplied to the two spherical cavitation chamber halves in order tocompress the brazing material and achieve a strong braze. In order toinsure that the inner surface of the completed cavitation chamber isrelatively smooth, means for aligning the two half spheres duringbrazing is required. The means can be integral to the half spheres, forexample alignment pins/holes. Alternately the means can be external tothe half sphere, for example an alignment jig.

In at least one embodiment of the invention, the cavitation chamber isfabricated from stainless steel and the brazing material is comprised ofnickel, chromium, silicon and boron. A force of approximately 1000 lbsis used during the brazing operation, the brazing temperature in therange of 1550° to 1650° F.

In at least one embodiment of the invention, after the cavitationchamber is finished, at least one acoustic transducer is coupled to thechamber in order to drive sonoluminescence within the chamber.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a spherical sonoluminescence cavitationchamber fabricated in accordance with the invention;

FIG. 2 is a cross-sectional view of a spherical cavitation chamberfabricated in accordance with the invention;

FIG. 3 illustrates the first step of chamber fabrication in which apiece of stock material is mounted within a lathe chuck;

FIG. 4 illustrates the step in which the inside surface of a sphericalchamber half is fabricated;

FIG. 5 illustrates the step in which a portion of the outside surface ofthe chamber half of FIG. 4 is fabricated;

FIG. 6 is a cross-sectional view of a chuck assembly in which the jawsare shaped to match the curvature of the outside surface of the chamberhalf shown in FIG. 5;

FIG. 7 is an end-view of the chuck assembly of FIG. 6;

FIG. 8 illustrates the chamber half of FIG. 5 mounted within the chuckassembly of FIGS. 6 and 7;

FIG. 9 illustrates the step in which the last remaining portion of thespherical chamber half of FIG. 4 is fabricated;

FIG. 10 illustrates the mounting of a larger stock piece in the lathechuck assembly in accordance with a second embodiment of the invention;

FIG. 11 illustrates the step in which the inside surface of a sphericalchamber half and a cylindrical portion are fabricated in accordance withthe second embodiment;

FIG. 12 illustrates the step of reversing the mounting configuration ofthe spherical chamber half in accordance with the second embodiment;

FIG. 13 illustrates the step in which the outside surface of thespherical chamber half of FIG. 11 is fabricated in accordance with thesecond embodiment;

FIG. 14 illustrates a pair of spherical chamber halves with a brazingmaterial interposed between the surfaces to be joined;

FIG. 15 is a frontal view of the ring of brazing material;

FIG. 16 illustrates the step of joining two half spheres, the halfspheres including alignment means;

FIG. 17 illustrates a preferred brazing jig;

FIG. 18 is a frontal view of a portion of the brazing jig shown in FIG.17;

FIG. 19 is a frontal view of a brazing jig with individual supportmembers;

FIG. 20 illustrates an alternate brazing jig with integral alignmentmeans; and

FIG. 21 is a graph of measured sonoluminescence data taken with a spherefabricated in accordance with the invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

FIG. 1 is an illustration of a spherical sonoluminescence cavitationchamber 101, hereafter referred to as simply a cavitation chamber,fabricated in accordance with the invention. In order to betterillustrate the mounting locations of the acoustic transducers in thisparticular embodiment, FIG. 1 includes centerlines 103–106. Mounted tothe exterior surface of cavitation chamber 101 are a total of 6 acoustictransducers, transducers 109–112 mounted to the lower hemisphere ofchamber 101 and transducers 115–116 mounted to the upper hemisphere ofchamber 101. It will be appreciated that the invention is not limited toa particular number or type of transducer, nor is the invention limitedto having transducers mounted to one or more particular locations.

FIG. 2 is a cross-sectional view of a spherical cavitation chamber 201fabricated in accordance with the invention. Chamber 201 has an outerspherical surface 203 defining the outer diameter of the chamber and aninner spherical surface 205 defining the inner diameter of the chamber.

Chamber 201 can be fabricated from any of a variety of metals althoughthere are some constraints placed on the chamber material. First, thematerial should be machinable. Second, if the chamber is to be operatedat a high temperature, the chamber material should have a relativelyhigh melting temperature. Additionally, a high melting temperature isuseful during the fabrication process when the two halves of the chamberare coupled. Third, the chamber material should be corrosion resistant,thus allowing the chamber to be used repeatedly. Fourth, the materialshould be hard enough to allow a good surface finish to be obtained. Inthe preferred embodiment of the invention, the chamber is fabricatedfrom 17-4 precipitation hardened stainless steel.

With respect to the dimensions of the chamber, both inner and outerdiameters, the selected sizes depend upon the intended use of thechamber. For example, smaller chambers are typically preferable forsituations in which it is desirable to limit the amount of cavitatingmedium, for example due to cost, or the applied energy (e.g., acousticenergy). On the other hand large chambers, on the order of 8–10 inchesor greater, typically simplify experimental set-up and eventobservation. Thick chamber walls are preferable if the chamber is to beoperated at high static pressures. Although the invention is not limitedto specific dimensions as previously noted, typical wall thicknessesinclude 0.25 inches, 0.5 inches, 0.75 inches, 1.5 inches, 2.375 inches,3.5 inches and 4 inches. Typical outside diameters are in the range of2–10 inches.

The preferred embodiment of the invention provides a means offabricating spherical chambers while at the same time minimizing wastedmaterial, and thus cost. The first step in the preferred method is tomount a piece 301 of the desired material into jaws 303 of lathe chuckassembly 304. The diameter 305 of piece 301 is preferably only slightlylarger than the desired chamber diameter, typically on the order of0.125 to 0.25 inches greater. Similarly, the length 307 is preferablyonly slightly larger than one half of the desired chamber diameter.

As illustrated in FIG. 4, the inside spherical surface 401 is thenfabricated (i.e., turned) to the desired diameter using the lathe. Ifdesired, a through hole 403 can be bored into piece 301 at this time.Next, without removing piece 301 from the lathe chuck, a portion 501 ofthe outer spherical surface is turned (FIG. 5). Additionally surface 503is turned while piece 301 is mounted within chuck assembly 304.

FIGS. 6 and 7 illustrate the preferred jaw assembly used during the nextphase of chamber fabrication. FIG. 6 is a cross-sectional view of lathechuck assembly 601 and FIG. 7 is an end view of chuck assembly 601.Although chuck assembly 601 is shown with 4 jaws 603, it will beappreciated that chuck assembly 601 could have fewer jaws (e.g., a 3 jawchuck) or more jaws (e.g., a 6 jaw chuck). Holding surfaces 605 of jaws603 are shaped such that they have a curvature that matches thecurvature of surface 501 of piece 301. Curving the surfaces of jaws 603provides a large contact area between jaws 603 and surface 501, thusspreading out the force applied to the chamber by the jaws. As a result,thinner wall thicknesses can be achieved without deforming the chamberwalls, a result that is difficult to achieve using standard,straight-faced jaws. Additionally this approach provides a strongermounting configuration, thus preventing piece 301 from being pulled outof chuck assembly 601, or moving within chuck assembly 601, during thefinal fabrication of the outer surface of the spherical chamber. It willbe appreciated that if piece 301 moves within the chuck assembly even bya minor amount, the finished chamber half will not have the preferredinside/outside spherical symmetry.

FIG. 8 illustrates piece 301 mounted in chuck assembly 601. During thefinal step of fabricating this spherical cavitation chamber half,surface 901 is turned as shown in FIG. 9.

Prior to chamber assembly, chamber surface 503 is finished flat.Assuming a chamber outside diameter of 10 inches or less, surface 503 isfinished flat to within at least ±0.01 inches, preferably within ±0.001inches, and still more preferably within ±0.0005 inches. For diametersgreater than 10 inches, the inventor has found that as a general rule,the finish surfaces previously noted are multiplied by a tenth ofdesired chamber's outside diameter (in inches). Thus for example,assuming a desired chamber diameter of 30 inches, the end surface wouldbe finished flat to within at least ±0.03 inches, preferably within±0.003 inches, and still more preferably within ±0.0015 inches.

Although preferably the spherical chamber halves are fabricated asdisclosed above, it will be understood that the inventor also envisionsminor variations of this fabrication technique. For example asillustrated in FIG. 10, dimension 307 of a stock piece 1001 can belarger than noted above with respect to FIG. 3. Then during the initialfabrication step (FIG. 11), a cylindrical portion 1003 is turned as wellas inside spherical surface 401.

Next, as illustrated in FIG. 12, piece 1001 is removed from chuckassembly 304, reversed, and mounted within chuck assembly 1201. Chuckassembly 1201 may be the same as chuck assembly 304 or may be different,for example having jaws 1203 which have the same curvature as that ofcylindrical portion 1003. The outside spherical surface 1301 is thenfabricated (i.e., turned) as shown in FIG. 13. If desired, at this pointthrough hole external features (i.e., pipe threads) can be added.

After turning outside surface 1301, the spherical chamber half isremoved from cylindrical portion 1003 along line 1303. Assuming achamber outside diameter of 10 inches or less, the end surface of thechamber half is then finished flat to within at least ±0.01 inches,preferably within ±0.001 inches, and still more preferably within±0.0005 inches. For diameters greater than 10 inches, the inventor hasfound that as a general rule, the finish surfaces previously noted aremultiplied by a tenth of desired chamber's outside diameter (in inches).Thus for example, assuming a desired chamber diameter of 30 inches, theend surface would be finished flat to within at least ±0.03 inches,preferably within ±0.003 inches, and still more preferably within±0.0015 inches.

In the preferred embodiment of the invention, the inner and outerspherical chamber surfaces are used as turned. It will be appreciated,however, that various surface finishing procedures (e.g., surfacegrinding or polishing) can be performed on either or both surfaces ifdesired.

Regardless of the exact method of fabricating the spherical chamberhalves, the next step is to join two halves to form the desiredcavitation chamber. As shown in FIG. 14, spherical chamber halves 1401and 1402 are ready to be joined. As illustrated, chamber half 1401includes a through hole while chamber half 1402 does not although aspreviously described, one or both chamber halves can include any numberof through holes or ports. Preferably any desired through holes or portsare completed prior to joining the chamber halves, thus insuring thatthe inner surfaces are finished and cleaned, a process that is moredifficult after the chamber halves have been joined.

After the surfaces to be mated, surfaces 1405 and 1407, are finished aspreviously described, they are ready to be joined, preferably using abrazing operation. The selection of the brazing material depends on thematerial comprising the half spheres. In the preferred embodiment inwhich the sphere is comprised of stainless steel, typical brazingmaterials are comprised of nickel and chromium with small percentages ofsilicon and boron. Such brazing materials can be obtained, for example,from Vacuum Process Engineering, Inc. in Sacramento, Calif. As numeroussuitable brazing materials are well known by those of skill in thebrazing industry, further detail is not provided herein.

Brazing material 1403 is preferably formed from a sheet, thus insuring acontinuous bond of uniform thickness. As can be seen in FIG. 15, brazingmaterial 1403 is preferably formed as a ring with approximately the samewidth 1501 as the wall thickness of the sphere. This approach provides abond of approximately the same width as the sphere walls, yielding aconsiderably stronger bond then simply bonding/welding around theperimeter of the sphere along the joint line. In the preferredembodiment the thickness of material 1403 is in the range of 0.0005 to0.0025 inches.

During the brazing operation, spherical cavitation chamber halves 1401and 1402 are pressed together with brazing material 1403 interposedbetween the half sphere surfaces as shown. The inventor has found that asuperior braze is formed by applying force in directions 1601 and 1602as shown in FIG. 16. Furthermore, preferably the brazing chamber isevacuated prior to heating the chamber halves and the brazing material.Assuming a vacuum brazing process is used as preferred, at least onethrough hole 403 must be included in at least one of the chamber halvesto allow pressure relief/equalization. Typically the brazing temperatureis on the order of 100° to 200° F. above the melting temperature of thebrazing material. In the preferred embodiment with a 9.5 inch outsidediameter sphere of 17-4 stainless steel, the brazing temperature is onthe order of 1550° to 1650° F. and the force applied in directions 1601and 1602 is preferably at least 1000 lbs.

During the joining process, spherical cavitation chamber halves 1401 and1402 are aligned to insure that the inner sphere surface does not have adiscontinuity at the seam line after fabrication. One process forinsuring alignment is to use two or more alignment pins 1603 withcorresponding holes 1605 as shown in FIG. 16. The inventor has foundthat if the coefficient of thermal expansion of alignment pins 1603 andthe spherical chamber halves differ greatly, alignment issues may ariseduring the brazing operation. Differences in thermal expansion may alsolead to sphere deformation. Accordingly in the preferred embodimentalignment pins 1603 are fabricated from the same material as that of thespherical chamber halves.

Minimizing surface deformation during the brazing operation is criticalto insure that the final chamber is a true sphere, a goal which becomesmore difficult to obtain as the brazing temperature and/or applied forceis increased, and as the chamber wall thickness is decreased.Accordingly a brazing jig 1701 is used in the preferred embodiment ofthe invention, wherein a first jig half 1703 applies force to chamberhalf 1401 and a second jig half 1705 applies force to chamber half 1402.In keeping with the goal of minimizing surface deformation, preferablyeach jig half contacts the corresponding chamber half over a relativelylarge surface area, thus distributing the applied force. Assuming avacuum brazing process is used as preferred, preferably jig halves 1703and 1705 each include a pressure relief through hole 1706.

Assuming a brazing jig is used rather than simply applying force on thetwo sphere halves, the invention does not require a specific brazing jigconfiguration. As previously noted, however, it is advantageous todistribute the applied force over as large an area as reasonable.Accordingly in the embodiment illustrated in FIG. 17, sphere contactsurfaces 1707 of jig portions 1703 and 1705 are bowl shaped with acurvature that corresponds to the curvature of spherical chamber halves1401 and 1402, respectively, thus spreading the force over a very largearea. In the illustrated embodiment, the central portion 1709 ofsurfaces 1707 is removed. It will be appreciated that portion 1709 neednot be removed, nor is the size of portion 1709 critical as long assufficient contact surfaces 1707 are provided to distribute the appliedforce. Preferably surfaces 1707 are continuous, i.e., a ring asillustrated in the frontal view of jig portion 1703 shown in FIG. 18.Note that surface 1707 shown in FIG. 18 has the central portion 1709removed as illustrated in the cross-sectional of FIG. 17.

In addition to allowing surfaces 1707 to be either a half of a sphere(i.e., bowl shaped) or a spherical ring (i.e., half of a sphere with acentral portion 1709 removed), surfaces 1707 can be comprised ofindividual support members. For example, FIG. 19 illustrates the frontalview of jig portion 1703 in which surface 1707 is divided into fourindividual support members 1901. Although maximizing surfaces 1707 ispreferred from the standpoint of distributing the force applied by thejig halves to the chamber halves, thus minimizing the risk ofdeformation, it will be appreciated that removing portions of surfaces1707 allow the addition of external features (e.g., tubes, diagnostics,etc.) to the chamber halves prior to performing the brazing process.

In the preferred embodiment of the invention, a layer 1715 of releasematerial is interposed between surfaces 1707 of brazing jig 1701 and theouter surfaces of chamber halves 1401 and 1402. Layer 1715 is used toaid in the removal of the brazed spherical chamber from jig portions1703 and 1705 by preventing accidental bonding via diffusion or brazingmaterial drips. Although any of a variety of high temperature metals canbe used, in the preferred embodiment in which the spherical chamber iscomprised of stainless steel, layer 1715 is comprised of a thin foil oftungsten.

As previously noted, during the brazing operation it is critical tomaintain the alignment of the spherical cavitation chamber halves tominimize surface discontinuities at the braze joint. Preferablyalignment pins integral to the chamber halves are used as previouslydescribed. Alternately the alignment means may be included in thebrazing jig. For example as illustrated in FIG. 20, surfaces 1711 and1713 of jig portions 1703 and 1705, respectively, include multiplealignment pins 2001 and corresponding holes 2003. It will be appreciatedthat even if the alignment means is integral to the chamber halves aspreferred and illustrated in FIGS. 16 and 17, it may be beneficial toinclude additional alignment means that are integral to the brazing jig.

FIG. 21 is a graph that illustrates the sonoluminescence effect with asphere fabricated in accordance with the invention. The sphere wasfabricated from stainless steel and had an outer diameter of 9.5 inchesand an inner diameter of 8 inches. Six acoustic drivers (i.e.,transducers) were mounted as illustrated in FIG. 1. For the data shownin FIG. 21, the liquid within the chamber was acetone. During operation,the temperature of the acetone was −27.5° C. The driving frequency was23.52 kHz, the driving amplitude was 59 V RMS, and the driving power was8.8 watts. Two acoustic cycles are shown in FIG. 21. It will beappreciated that the data shown in FIG. 21 is only provided forillustration, and that the invention is not limited to this specificconfiguration.

As will be understood by those familiar with the art, the presentinvention may be embodied in other specific forms without departing fromthe spirit or essential characteristics thereof. Accordingly, thedisclosures and descriptions herein are intended to be illustrative, butnot limiting, of the scope of the invention which is set forth in thefollowing claims.

1. A method of fabricating a cavitation chamber comprising the steps: a)mounting a piece of stock material in a first lathe chuck; b) finishinga first mating surface of a first half sphere; c) turning an internalspherical surface corresponding to an inside surface of said first halfsphere; d) turning a first portion of an external surface of said firsthalf sphere; e) dismounting said piece of stock material and reversing amounting position of said piece of stock material relative to a firstlathe chuck position; f) mounting said piece of stock material in asecond lathe chuck; g) turning a second portion of said external surfaceof said first half sphere; h) repeating steps a) through g) with asecond piece of stock material to form a second half sphere, said secondhalf sphere having a second mating surface, both said first and secondhalf spheres having a first inner diameter and a first outer diameter;i) locating a ring-shaped sheet of brazing material between said firstand second mating surfaces, said ring-shaped sheet having a second innerdiameter approximately equivalent to said first inner diameter, and saidring-shaped sheet having a second outer diameter approximatelyequivalent to said first outer diameter; and j) brazing said first andsecond mating surfaces together.
 2. The method of fabricating thecavitation chamber of claim 1, wherein step b) is performed after stepd).
 3. The method of fabricating the cavitation chamber of claim 1,wherein step b) is performed after step g).
 4. The method of fabricatingthe cavitation chamber of claim 1, further comprising the step of boringa through-hole in said first half sphere, wherein said boring step isperformed before step e).
 5. The method of fabricating the cavitationchamber of claim 1, further comprising the step of boring a through-holein said first half sphere, wherein said boring step is performed afterstep g).
 6. The method of fabricating the cavitation chamber of claim 1,wherein step d) is performed before step c).
 7. The method offabricating the cavitation chamber of claim 1, wherein said externalsurface of said first half sphere has a first curvature, and whereinsaid step of mounting within said second lathe chuck further comprisesthe step of selecting a second lathe chuck with a plurality of jaws,wherein each jaw of said plurality of jaws has a holding surface with asecond curvature matching said first curvature.
 8. The method offabricating the cavitation chamber of claim 1, wherein said first andsecond lathe chucks are the same.
 9. The method of fabricating thecavitation chamber of claim 1, wherein said finishing step comprisesobtaining a surface flatness of within ±0.01 inches.
 10. The method offabricating the cavitation chamber of claim 1, wherein said finishingstep comprises obtaining a surface flatness of within ±0.001 inches. 11.The method of fabricating the cavitation chamber of claim 1, whereinsaid finishing step comprises obtaining a surface flatness of within±0.0005 inches.
 12. The method of fabricating the cavitation chamber ofclaim 1, further comprising the step of selecting said piece of stockmaterial from an alloy.
 13. The method of fabricating the cavitationchamber of claim 12, wherein said alloy is a stainless steel alloy. 14.The method of fabricating the cavitation chamber of claim 1, furthercomprising the step of maintaining a thickness of said ring-shaped sheetof brazing material of between 0.0005 and 0.0025 inches prior to saidbrazing step.
 15. The method of fabricating the cavitation chamber ofclaim 1, said brazing step further comprising the step of evacuating aheating chamber used during said brazing step.
 16. The method offabricating the cavitation chamber of claim 1, said brazing step furthercomprising the step of applying compressive force to said first andsecond half spheres.
 17. The method of fabricating the cavitationchamber of claim 16, wherein said compressive force is at least 1000lbs.
 18. The method of fabricating the cavitation chamber of claim 1,wherein said brazing step is performed at a temperature of approximately100° to 200° F. above a melting temperature of said brazing material.19. The method of fabricating the cavitation chamber of claim 1, furthercomprising the steps: k) mounting at least one alignment pin in saidfirst mating surface; l) boring at least one hole corresponding to saidat least one alignment pin in said second mating surface; and m)aligning said at least one alignment pin and said at least onecorresponding hole prior to said brazing step j).
 20. The method offabricating the cavitation chamber of claim 1, further comprising thestep of positioning said first and second half spheres in a brazing jigprior to performing said brazing step j).
 21. A method of fabricating acavitation chamber comprising the steps: a) mounting a piece of stockmaterial in a lathe chuck; b) turning an internal spherical surfacecorresponding to an inside surface of a first half sphere; c) forming acylindrical end portion on said piece of stock material; d) dismountingsaid piece of stock material and reversing a mounting position of saidpiece of stock material relative to said lathe chuck; e) remounting saidpiece of stock material into said lathe chuck; f) turning an externalspherical surface corresponding to an outside surface of said first halfsphere; g) removing excess stock material from said first half sphere;h) finishing a first mating surface of said first half sphere; i)repeating steps a) through h) with a second piece of stock material toform a second half sphere, said second half sphere having a secondmating surface, both said first and second half spheres having a firstinner diameter and a first outer diameter; j) locating a ring-shapedsheet of brazing material between said first and second mating surfaces,said ring-shaped sheet having a second inner diameter approximatelyequivalent to said first inner diameter, and said ring-shaped sheethaving a second outer diameter approximately equivalent to said firstouter diameter; and k) brazing said first and second mating surfacestogether.
 22. The method of fabricating the cavitation chamber of claim21, wherein step c) is performed before step b).
 23. The method offabricating the cavitation chamber of claim 21, further comprising thestep of boring a through-hole in said first half sphere, wherein saidboring step is performed before step d).
 24. The method of fabricatingthe cavitation chamber of claim 21, further comprising the step ofboring a through-hole in said first half sphere, wherein said boringstep is performed before step i).
 25. The method of fabricating thecavitation chamber of claim 21, wherein said finishing step comprisesobtaining a surface flatness of within ±0.01 inches.
 26. The method offabricating the cavitation chamber of claim 21, wherein said finishingstep comprises obtaining a surface flatness of within ±0.001 inches. 27.The method of fabricating the cavitation chamber of claim 21, whereinsaid finishing step comprises obtaining a surface flatness of within±0.0005 inches.
 28. The method of fabricating the cavitation chamber ofclaim 21, further comprising the step of selecting said piece of stockmaterial from an alloy.
 29. The method of fabricating the cavitationchamber of claim 28, wherein said alloy is a stainless steel alloy. 30.The method of fabricating the cavitation chamber of claim 21, furthercomprising the step of maintaining a thickness of said ring-shaped sheetof brazing material of between 0.0005 and 0.0025 inches prior to saidbrazing step.
 31. The method of fabricating the cavitation chamber ofclaim 21, said brazing step further comprising the step of evacuating aheating chamber used during said brazing step.
 32. The method offabricating the cavitation chamber of claim 21, said brazing stepfurther comprising the step of applying compressive force to said firstand second half spheres.
 33. The method of fabricating the cavitationchamber of claim 32, wherein said compressive force is at least 1000lbs.
 34. The method of fabricating the cavitation chamber of claim 21,wherein said brazing step is performed at a temperature of approximately100° to 200° F. above a melting temperature of said brazing material.35. The method of fabricating the cavitation chamber of claim 21,further comprising the steps: l) mounting at least one alignment pin insaid first mating surface; m) boring at least one hole corresponding tosaid at least one alignment pin in said second mating surface; and n)aligning said at least one alignment pin and said at least onecorresponding hole prior to said brazing step j).
 36. The method offabricating the cavitation chamber of claim 21, further comprising thestep of positioning said first and second half spheres in an alignmentjig prior to performing said brazing step k).
 37. A method offabricating a cavitation system comprising the steps: a) mounting apiece of stock material in a first lathe chuck; b) finishing a firstmating surface of a first spherical cavitation chamber half; c) turningan internal spherical surface corresponding to an inside surface of saidfirst spherical cavitation chamber half; d) turning a first portion ofan external surface of said first spherical cavitation chamber half,wherein said external surface of said first spherical cavitation chamberhalf has a first curvature; e) dismounting said piece of stock materialand reversing a mounting position of said piece of stock materialrelative to a first lathe chuck position; f) mounting said piece ofstock material in a second lathe chuck, wherein said second lathe chuckhas a plurality of jaws, wherein each jaw of said plurality of jaws hasa holding surface with a second curvature matching said first curvature;g) turning a second portion of said external surface of said firstspherical cavitation chamber half; h) repeating steps a) through g) witha second piece of stock material to form a second spherical cavitationchamber half, said second spherical cavitation chamber half having asecond mating surface, both said first and second spherical cavitationchamber halves having a first inner diameter and a first outer diameter;i) locating a ring-shaped sheet of brazing material between said firstand second mating surfaces, said ring-shaped sheet having a second innerdiameter approximately equivalent to said first inner diameter, and saidring-shaped sheet having a second outer diameter approximatelyequivalent to said first outer diameter; j) aligning said first andsecond spherical cavitation chamber halves; and k) brazing said firstand second mating surfaces together; and l) coupling at least oneacoustic transducer to said external spherical surface.
 38. The methodof fabricating the cavitation chamber of claim 37, wherein step b) isperformed after step d).
 39. The method of fabricating the cavitationchamber of claim 37, wherein step b) is performed after step g).
 40. Themethod of fabricating the cavitation chamber of claim 37, furthercomprising the step of boring a through-hole in said first sphericalcavitation chamber half, wherein said boring step is performed beforestep e).
 41. The method of fabricating the cavitation chamber of claim37, further comprising the step of boring a through-hole in said firstspherical cavitation chamber half, wherein said boring step is performedafter step g).
 42. The method of fabricating the cavitation chamber ofclaim 37, wherein step d) is performed before step c).
 43. The method offabricating the cavitation system of claim 37, wherein said finishingstep comprises obtaining a surface flatness of at least ±0.01 inches.44. The method of fabricating the cavitation system of claim 37, furthercomprising the step of selecting said piece of stock material from analloy.
 45. The method of fabricating the cavitation system of claim 44,wherein said alloy is a stainless steel alloy.
 46. The method offabricating the cavitation system of claim 37, further comprising thestep of maintaining a thickness of said ring-shaped sheet of brazingmaterial of between 0.0005 and 0.0025 inches prior to said brazing step.47. The method of fabricating the cavitation system of claim 37, saidbrazing step further comprising the step of evacuating a heating chamberused during said brazing step.
 48. The method of fabricating thecavitation system of claim 37, said brazing step further comprising thestep of applying compressive force to said first and second sphericalcavitation chamber halves.
 49. The method of fabricating the cavitationsystem of claim 37, wherein said brazing step is performed at atemperature of approximately 100° to 200° F. above a melting temperatureof said brazing material.
 50. The method of fabricating the cavitationsystem of claim 37, said aligning step further comprising the steps: m)mounting at least one alignment pin in said first mating surface; n)boring at least one hole corresponding to said at least one alignmentpin in said second mating surface; and o) aligning said at least onealignment pin and said at least one corresponding hole prior to saidbrazing step k).
 51. The method of fabricating the cavitation system ofclaim 37, said aligning step further comprising the step of positioningsaid first and second spherical cavitation chamber halves in a brazingjig prior to performing said brazing step k).
 52. A method offabricating a cavitation system comprising the steps: a) mounting apiece of stock material in a lathe chuck; b) turning an internalspherical surface corresponding to an inside surface of a firstspherical cavitation chamber half; c) forming a cylindrical end portionon said piece of stock material; d) dismounting said piece of stockmaterial and reversing a mounting position of said piece of stockmaterial relative to said lathe chuck; e) remounting said piece of stockmaterial into said lathe chuck; f) turning an external spherical surfacecorresponding to an outside surface of said first spherical cavitationchamber half; g) removing excess stock material from said firstspherical cavitation chamber half; h) finishing a first mating surfaceof said first spherical cavitation chamber half; i) repeating steps a)through h) with a second piece of stock material to form a secondspherical cavitation chamber half, said second spherical cavitationchamber half having a second mating surface, both said first and secondspherical cavitation chamber halves having a first inner diameter and afirst outer diameter; j) locating a ring-shaped sheet of brazingmaterial between said first and second mating surfaces, said ring-shapedsheet having a second inner diameter approximately equivalent to saidfirst inner diameter, and said ring-shaped sheet having a second outerdiameter approximately equivalent to said first outer diameter; k)aligning said first and second spherical cavitation chamber halves; l)brazing said first and second mating surfaces together; and m) couplingat least one acoustic transducer to said external spherical surface. 53.The method of fabricating the cavitation chamber of claim 52, whereinstep c) is performed before step b).
 54. The method of fabricating thecavitation chamber of claim 52, further comprising the step of boring athrough-hole in said first spherical cavitation chamber half, whereinsaid boring step is performed before step d).
 55. The method offabricating the cavitation chamber of claim 52, further comprising thestep of boring a through-hole in said first spherical cavitation chamberhalf, wherein said boring step is performed before step i).
 56. Themethod of fabricating the cavitation system of claim 52, wherein saidfinishing step comprises obtaining a surface flatness of at least ±0.01inches.
 57. The method of fabricating the cavitation system of claim 52,further comprising the step of selecting said piece of stock materialfrom an alloy.
 58. The method of fabricating the cavitation system ofclaim 57, wherein said alloy is a stainless steel alloy.
 59. The methodof fabricating the cavitation system of claim 52, further comprising thestep of maintaining a thickness of said ring-shaped sheet of brazingmaterial of between 0.0005 and 0.0025 inches prior to said brazing step.60. The method of fabricating the cavitation system of claim 52, saidbrazing step further comprising the step of evacuating a heating chamberused during said brazing step.
 61. The method of fabricating thecavitation system of claim 52, said brazing step further comprising thestep of applying compressive force to said first and second sphericalcavitation chamber halves.
 62. The method of fabricating the cavitationsystem of claim 52, wherein said brazing step is performed at atemperature of approximately 100° to 200° F. above a melting temperatureof said brazing material.
 63. The method of fabricating the cavitationsystem of claim 52, said aligning step further comprising the steps of:n) mounting at least one alignment pin in said first mating surface; o)boring at least one hole corresponding to said at least one alignmentpin in said second mating surface; and p) aligning said at least onealignment pin and said at least one corresponding hole.
 64. The methodof fabricating the cavitation system of claim 52, said aligning stepfurther comprising the step of positioning said first and secondspherical cavitation chamber halves in an alignment jig.